#include <iostream>
#include <vector>
#include <queue>
using namespace std;

//https://www.nowcoder.com/practice/54ab9865ce7a45968b126d6968a77f34?tpId=196&tqId=40529&ru=/exam/oj

class Solution 
{
    int m, n;
    int dx[4] = { 0, 0, 1, -1 };
    int dy[4] = { 1, -1, 0, 0 };
    bool vis[1010][1010] = { 0 };
public:
    int rotApple(vector<vector<int> >& grid) 
    {
        m = grid.size(), n = grid[0].size();

        queue<pair<int, int>> q;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (grid[i][j] == 2)
                    q.push({ i, j });

        int ret = 0;
        while (q.size())
        {
            int sz = q.size();
            ret++;
            while (sz--)
            {
                auto [a,b] = q.front();
                q.pop();
                for (int i = 0; i < 4; i++)
                {
                    int x = a + dx[i], y = b + dy[i];
                    if (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1 && !vis[x][y])
                    {
                        vis[x][y] = true;
                        q.push({ x, y });
                    }
                }


            }
        }
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (grid[i][j] == 1 && !vis[i][j])
                    return -1;

        return ret - 1;
    }
};

int main()
{

	return 0;
}